Sergey Gortschakow

An Improved Arc Model Based on the Arc Diameter

This paper introduces an improved electrical arc model based on the arc diameter variation. In the conventional arc models, the arc diameter is considered as an implicit parameter in arc model constants. In case of decreasing arc diameter along with the arc extinction, the arc voltage decreases as well. The arc diameter can be implemented as a function of current into the arc model. The results illustrate that by applying the arc diameter as a function of arc current in the arc model, the simulated arc voltage is much closer to the measured values. In particular, the arc voltage behavior at the zero crossing can be controlled more precisely. However, based on the model considered for the arc diameter, additional parameters of the arc model should be estimated using measured data. The results confirm that even applying a simple arc diameter model can improve the arc voltage simulation.

Video Spectroscopy of Vacuum Arcs During Transition Between Different High-Current Anode Modes

This paper presents spectroscopic results of high-current anode phenomena in a vacuum arc discharge between CuCr electrodes. AC (alternative current) 50-Hz and 10-ms pulsed dc (direct current) are applied as interrupting current. Time and space resolved optical emission spectroscopy (video spectroscopy) is used to examine the temporal and spatial distribution of different atomic and ionic copper lines. During the transition from low-current mode to different high-current modes, including footpoint, anode spot, and intense arc mode, the intensity of Cu I, Cu II, and Cu III line radiation is examined near the anode, the cathode, and in the interelectrode gap. The results show that during the formation of anode spot and intense mode the intensity and the distribution of all lines change noticeably in the different spectral regions. In fact, higher ionization states represent the arc dynamics behavior during transition to high-current anode modes. Significant differences have been found, for example, in the spatial structure of Cu II and Cu III lines in the anode spot mode. The results for Cu I lines indicate an active role of atoms together with the ions in different charge states in high-current anode modes. The impact of threshold current and transferred charge of the formation of high-current anode modes in case of ac and pulsed dc is also investigated regarding the intensity of copper lines near the anode.

Impact of Different Vacuum Interrupter Properties on High-Current Anode Phenomena

This paper presents the impact of current waveform and frequency on the formation of high-current anode phenomena in a vacuum interrupter experiment. Different waveforms including the alternative current pulses of 50, 180, and 260 Hz and direct current pulses of 5 and 10 ms are compared. The impact of different opening times and contact speeds on the high-current anode mode formation is investigated. The results show that both instantaneous current and total transferred charge are important in the formation of high-current anode modes. Therefore, the arcing time has a strong influence. Two types of anode spot modes with different electrical and optical characteristics are also observed. The transitions between different high-current modes are examined systematically, resulting in existence areas dependent on threshold current and gap length. The latter are determined for different contact materials including Cu, CuCr7525, and CuCr50 and different contact diameters.

Fast video registration of transition processes from diffuse mode to anode spot mode in high-current arc with copper-chromium electrodes

Transition process from a diffuse to anode spot mode in high-current vacuum arc discharge with Cu-Cr electrodes has been studied experimentally. Images of the arc were recorded with a frequency of about 25000 frames per second synchronously with the acquisition of current and voltage waveforms. Experiments clarify that after the current reaches a certain threshold value (4 to 5 kA for bulk-type, 2-cm electrodes), the arc discharge passes from diffuse mode to the mode with anode spot and voltage increased by ~20 V. In this mode, bright anode jet appears; cathode micro spots are reduced in number and grouped in front of the anode jet with the formation the cathode macro spot. In such a threshold regime, the discharge can change to the anode-spot mode and back to diffuse mode many times, with transition time in the microsecond range. With increasing current amplitude, anode spot mode becomes more stable, cathode and anode macro-jets are coming closer together forming a quasi-continuous radially-constricted discharge channel. The constriction of discharge is accompanied by increasing power density on both electrodes. In the case of TMF type electrodes, the constricted plasma channel moves azimuthally along the electrode lobe.

Influence of paper properties on streamers creeping in mineral oil

This work presents an experimental study of second mode positive streamers propagating along mineral oilpaper interfaces. A point-plane arrangement immersed in mineral oil with the paper inclined 60 degrees to the plane electrode is used to create the liquid-solid interface. Kraft paper and a kraft fibril paper, made from cellulosic micro and nano fibrils, with higher density and lower surface roughness are used as the solid materials. High speed shadowgraphy and charge recordings are used to compare the propagation of second mode positive streamers along the mineral oil-kraft paper and mineral oil-kraft fibril paper. Streamers creeping along the mineral oil-kraft paper interface propagate mainly into the liquid, with one or two main filaments. In comparison, the streamers propagating along the kraft fibril paper show a strong reduction of the branching; these streamers consist of a single filament that propagates exactly on the solid surface. Streamers along the kraft fibril paper also have longer propagation time than for the case with kraft paper. Mutual electrostatic shielding between filaments is observed for the streamers creeping on the kraft paper. An electrostatic analysis of the influence of permittivity, density and surface roughness of the solid in the electrical properties of the streamer filaments is also performed.

Anode Surface Temperature Determination in High-Current Vacuum Arcs by Different Methods

The electrode surface temperatures of Cu–Cr butt electrodes exposed to vacuum arcs with sinusoidal currents of 10–20 kA and under external axial magnetic field were determined. Different experimental techniques were applied that can be distinguished by the used spectral wavelength range, their temporal, and spatial resolution. Near infrared spectroscopy was carried out by means of a fiber optic spectrometer working in the wavelength range from 900 to 1670 nm with a temporal resolution of 1–2 ms. Electrode surface temperatures after current zero were obtained from the relative shape of the spectrum using the Planck curve fitting procedure. Furthermore, electrode emissivities were derived after performing absolute calibration of the spectra. Pyrometric measurements were performed in the spectral range around 2

Determination of Cr Density After Current Zero in a High-Current Vacuum Arc Considering Anode Plume

\mu \text{m}

Numerical investigation of transient, low-power metal vapour discharges occurring in near limit ignitions of flammable gas.

with high temporal but without spatial resolution. 2-D distributions of the electrode temperature were obtained from high-speed video thermography using a camera with a metal interference filter at 890 nm.